Times Tables and Repunit Numbers

I bet anything you like (well, not a million pounds, perhaps) you have never heard of Repunit numbers and I also bet you are absolutely fascinated to find out what they are.

Before you can see what type of number they are, you are going to have to do some big sums using (you guessed it!), your multiplication tables again.

Try these sums and see what you notice about the answers:

NO CALCULATORS.

1.      41 x 271

2.      3 x 7 x 11 x 13 x 37

3.      239 x 4649

4.      513239 x 21649

5.      (If you still have some energy left you can try this one)

                                 5363222357 x 2071723  (Yikes!)

Now can you see what Repunit numbers are (assuming you didn’t make any mistakes with the multiplications, of course). If you still haven’t worked it out, divide the word Repunit into two parts.

To work out some of the very large Repunit numbers you would need a good computer, but you might be able to work out a few that are smaller than the ones I have given here.

Can you find multiplication sums for the first 4 Repunit numbers?